Color Management panel in Blender
The CM panel is somewhat confusing due to some unfortunate labelling.


  Now it seems to me that I have two options for Display Device in the
  Color Management Panel, either sRGB or None. I guess the color space
  for the monitor will be sRGB when I chose sRGB ?


Display Device is nothing more than a collection of View transforms. Think of it as a grouping.


  What happens when I chose none ? Will I see the linear color space


Close but not quite. You will see whatever the reference space sees. If you assign a different colour space to an image in the UV Viewer for example, you will see whatever you have set the image to, as transformed to reference. If you properly linearize a display referred sRGB to display linear via a correct transform, you would see those values dumped directly to display. In the case of a typical LCD panel however, we have to remember that such electronic displays, though they operate almost strictly linearly, will have a 2.2 power curve baked into their lower level hardware. So the not-so-simple answer is that you would be seeing display linear values dumped to a 2.2 power curve in all likelihood.


  I guess under normal circumstances there are no reasons to correct
  exposure or Gamma ? When would this be useful ?


One could correct exposure via the exposure control, however in most typical situations, the two controls are used to check compositing. Bending values can reveal problematic keys, comps, and other details, as well as previewing looks / creative grades, and how materials respond.


  When choosing "Default" this means "Does no extra conversion besides
  the conversion for the display device.". That seems fine to me.


Default is simply a label. It is the sRGB specification's transfer curve. While default, the sRGB transfer curve was never intended for rendering, and has many implications. See some of my other answers on wide dynamic range for further information.


  Is this about rendering image sequences ? Or video editing ? I am not
  sure what is meant here.


This is a byproduct of the VSE being hacked around how OpenColorIO was designed to work. It is how the VSE sees image data in its reference. That is, it is a hack around how OCIO was designed to give the VSE a unique reference space.